Words related to inexpressible
In Old French and Middle English often en-, but most of these forms have not survived in Modern English, and the few that do (enemy, for instance) no longer are felt as negative. The rule of thumb in English has been to use in- with obviously Latin elements, un- with native or nativized ones.
late 14c., "represent in visual arts; put into words," from Old French espresser, expresser "press, squeeze out; speak one's mind" (Modern French exprimer), Medieval Latin expressare, frequentative of Latin exprimere "represent, describe, portray, imitate, translate," literally "to press out" (source also of Italian espresso); the sense evolution here perhaps is via an intermediary sense such as "clay, etc., that under pressure takes the form of an image," from ex "out" (see ex-) + pressare "to press, push," from Latin premere "to press, hold fast, cover, crowd, compress" (from PIE root *per- (4) "to strike"). Related: Expressed; expresses; expressing; expressible.
1726, from in- (1) "not, opposite of" + describable. Related: Indescribably; indescribability (1797). In same sense, Old English had unasecgendlic. Indescribables for "trousers" (1819) was colloquial in England for a generation or so.
We cannot omit here to state, that, some years since, we recollect a rumour in the gallery [of the House of Commons], that Madame de Staël was sitting, en habit d'homme, in a surtout and military indescribables, listening to the debate, under the protection of Sir J. Macintosh. ["Privileges of Women," in Retrospective Review, London, 1824]
As a noun, "indispensable thing," from 1794; c. 1800-1810, after French use, it was the name of a type of pocket bag worn by women. indispensables (1820) also was one of the many 1820s jocular euphemisms for "trousers" (see inexpressible). Related: Indispensably.
Meaning "that may not be spoken" is from 1590s. Plural noun ineffables was, for a time, a jocular euphemism for "trousers" (1823; see inexpressible). Related: Ineffably.
"unnameable," late 14c., from Old French innominable, from Late Latin innominabilis "that cannot be named," from in- "not, opposite of" (see in- (1)) + *nominabilis, from Latin nominalis "pertaining to a name or names," from nomen (genitive nominis) "name" (from PIE root *no-men- "name"). In jocular use, innominables = "trousers" (1827; see inexpressible).